Formation of a novel CdS cluster in an organic multilayer template: A case of an organic/inorganic superlattice

A highly ordered multilayer film was formed by casting the aqueous dispersion of an ethylenediamine-containing double-chain amphiphile 1. Dipping of the cast film in aqueous cadmium halides led to incorporation of specific amounts of CdCl₂ or CdBr₂ without losing the regular multibilayer structure, as confirmed by differential scanning calorimetry and reflection X-ray diffraction. Elemental composition determined by X-ray photoelectron spectroscopy and ¹¹³Cd MAS-NMR spectroscopy indicated the presence of tetrahedral structures of CdCl₄^2- and CdBr₃^- species coordinated by amphiphile 1. Upon exposure of the 1₂-CdCl₄ composite film to H₂S gas at room temperature, Q-state CdS particles (size, ∼30 Å) were formed. In the case of the 1-CdBr₃ composite film, one sulfur atom was introduced per four Cd²⁺ ions without substantial changes in the coordination structure. This indicates that a novel Cd-Br-S cluster was formed in the interbilayer space of preorganized amphiphilic ligands. The multibilayer cast film serves as a molecular template for controlled synthesis of novel organic/inorganic superlattices.